Tamerlan Tsarnaev, 26, left, and Dzhokhar Tsarnaev, 19. / AP

by Anna G. Arutunyan, Special for USA TODAY

by Anna G. Arutunyan, Special for USA TODAY

MOSCOW - Russians appeared shocked and bewildered by the revelation that the Boston bombing suspects have ties to the region.

"(Dzhokhar Tsarnaev) was just a boy, I felt sorry for him, and I don't believe that he came up with all this on his own," said Tatyana Ivanova, a Moscow entrepreneur in her 30s. "When I found out about it, my first thought was that it was a provocation, or that these two guys became really confused, or simply went insane."

The two suspects in last week's Boston Marathon bombing were identified as Tamerlan Tsarnaev, 26, and his brother, Dzhokhar Tsarnaev, 19, ethnic Chechens who had lived in the United States for the last decade. Before immigrating, they had lived in the former Soviet republic of Kyrgyzstan and had also traveled to Russia's restive North Caucasus region.

A Russian law enforcement official, speaking with the state-owned RIA Novosti news agency, denied a direct link between the Tsarnaev brothers and Chechen extremist groups, such as the Caucasus Emirates, headed by a Chechen Islamist Doku Umarov.

The official, who didn't want to be named because he was not authorized to speak publicly on the matter, said the suspects' names did not appear in a law enforcement database tied to Umarov's group.

U.S. investigators were looking into a potential connection to North Caucasus extremist groups, such as the Caucasus Emirate, after discovering the contents of slain suspect Tamerlan Tsarnaev's YouTube account, Fox News reported.

Earlier it emerged that a foreign government had given the FBI information about Tamerlan Tsarnaev being a follower of radical Islam, according to an FBI news release. According to two law enforcement officials cited by the Associated Press, the information came from Russia's security service, the FSB.

"I don't think it's realistic for Doku Umarov to consider attacking America, he is relatively weak right now," said Oleg Orlov, chairman of the Memorial Human Rights Society, who has worked extensively in Chechnya. "But on the other hand, they position themselves as part of a fundamentalist Islamic movement. Ideologically, there could be some sense of unity" with the Tsarnaev brothers.

After the breakup of the Soviet Union in 1991, Russia staged two wars to rein in the predominantly Muslim, separatist province of Chechnya, located in the mountainous region of the North Caucasus. But if the first conflict in the 1990s was staged primarily against nationalist separatists, the second military operation in 1999-2000 and the insurgency that followed largely fought against militant Islamist cells that included various nationalities in the region, such as the Dagestani and the Ingush, experts say.

"It's not really appropriate here to draw on the Chechen ethnic identity. What's important is not that they are Chechens, but that they are (radical) Muslims," Orlov said. "This jihadist movement doesn't really differentiate between (North Caucasus nationalities). This is the difference between the former Chechen separatism movement."

Extremist groups denied responsibility and condemned the attacks.

"The command of the Dagestan Vilayat states that Caucasian mujahedeen do not engage in military action with the United States of America," said a statement from the extremist Dagestan Viyalat group, which was reportedly linked in Tsarnaev's YouYube account.

The statement was posted on the Kavkaz Center website. "We fight with Russia, which is responsible not only for the occupation of the Caucasus, but for heinous crimes against Muslims. Even in regards to the enemy state of Russia, with which the Imarat Kavkaz (Caucasus Emirate) does battle, there is an order in effect from the Amir of the (Imarat Kavkaz) Doku Umarov, which forbids attacks on civilian targets."

However, Umarov, a warlord who has earned the nickname of Russia's Osama bin Laden, has in the past taken responsibility for a number of terrorist attacks on Russian soil, most notably the January 2011 bombing at Moscow's Domodedovo Airport, and the subway bombings in Moscow in March 2010, which claimed the lives of 40 people.

"For me, there's no clear link between (the Tsarnaevs) and the terrorist underground," military expert Vladislav Shurygin told Russkaya Sluzhba Novostei (Russian Radio Service), a radio station in Moscow.

"But it's clear that the terror attack was connected to them wanting to play. The Internet (is) responsible. They just started browsing the Internet, found some sites connected to extremist activity, and decided to show off."